Such an input device is already known from U.S. Pat. No. 4,633,227. This type of input device, having the shape of a computer keyboard, has keys which which allow to see a display means made of plastic and which is situated below them. Using a handwheel, the display means can be placed into different positions. According to the position, different areas of the display means become visible, so that different keyboard layouts can be achieved. It is also possible to take out and turn around the display means in order to add further layouts. The position of the hand wheel indicates which layout has been chosen, so that the corresponding key signals can be transmitted to a connected computer.
A further, similar input device is already known from US patent application US 2003/0128191 A1. This document describes an input device with a regular computer screen that a transparent keyboard is assigned to. One portion of the computer screen is reserved for the transparent keyboard. This portion has touch-screen functionality and features raised, springy keys. When pressing keys, the user receives a feedback. Besides optical and possibly acoustic notifications, there is also an additional haptic or tactile feedback. Because the transparent keys are partially located above the screen, symbols can be displayed underneath the keys. These symbols can be perceived by the user through the surface of the keys. The symbol identifies the function of the key located directly above itself. Therefore, updated functionality of the keys can be accompanied by a change of display, effectively adapting the key labels.
Another related device is shown in German patent publication DE 40 17 897 C1. It discloses a control device for a vehicle. Here, single keys and/or a slide control are located above a display on which the possible functions of the switching means above are displayed.
The fundamental problem is therefore that multiple functions may be assigned to one key, partially also dependent on the software in use, and that said functions are not necessarily discernable by the user. Hence, when using common keyboards or switching elements, the user has to know in advance the different key combinations and underlying functions, or otherwise he may need to look them up or learn them by trial and error.
In this light one has to consider German patent application DE 83 03 605 from 1983. It proposes the use of an adjustable barrel by the aid of which different functions can be assigned to special function keys provided for this purpose. According to the position of the barrel, each key is assigned a different function which is displayed on the barrel, visible behind a viewing panel. Besides changing the functionality of the keys, by turning the adjustable barrel, it is also possible to effect a change of the display above said keys.
Another advancement can be seen in German patent application DE 35 32 327 A1, wherein a writing automaton with alterable keys is presented. The keys exhibit segment displays which are supposed to represent values assigned to the respective keys. However, by employing segment displays, the range of symbols which can be represented is considerably restricted.
German patent DE 10 2005 025 301 B4 allows for a much higher degree of freedom. It describes an input device which can, in one possible variant, consist of a common keyboard and a touchscreen area, one half each. Accordingly, the touchscreen area can be used as an extension of the common keyboard and thus provides an area for adjustable allocation and usage.
Finally, German patent application DE 10 2007 016 703 A1 from the same field presents a medical appliance with an input device. Here, the keys and the area located around them, respectively, are equipped with a display. This display is to be realized by use of either electronic ink or by means of an LC display.